[Refactor] Use RayClusterHeadPodsAssociationOptions to replace MatchingLabels

[evalaiyc98]

Why are these changes needed?

This PR aims to follow up issue#2045. The purpose of this initiative is to maintain consistency in association methods and avoid scattering MatchingLabels usage throughout the entire codebase. In this PR, I focus on updating the suite_helpers_test.go file to reflect this change.

Related issue number

2045

Checks

• [x] I've made sure the tests are passing.
• Testing Strategy
  • [x] Unit tests
  • [x] Manual tests
  • [ ] This PR is not tested :(